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Biodegradation of free cyanide by bacterial species isolated from cyanide-contaminated artisanal gold mining catchment area in Burkina Faso

IWRA World Water Congress 2017 - Cancun Mexico
2. Water quality, wastewater and reuse
Author(s): Lovasoa Christine RAZANAMAHANDRY
Harinaivo Anderson ANDRIANISA
Hela KAROUI
Hamma YACOUBA

Lovasoa Christine RAZANAMAHANDRY
International Institute for Water and Environmental Engineering (2iE)
tantely1989@gmail.com
Harinaivo Anderson ANDRIANISA
International Institute for Water and Environmental Engineering (2iE)
anderson.andrianisa@2ie-edu.org
Hela KAROUI
International Institute for Water and Environmental Engineering (2iE)
hela.karoui@2ie-edu.org
Hamma YACOUBA
International Institute for Water and Environmental Engineering (2iE)
hamma.yacouba@2ie-edu.org


Keyword(s): Soil, Water, Cyanide, Contamination, Bioremediation
Article:

Abstract

Soil and water samples were collected from a watershed in Burkina Faso where illegal artisanal gold extraction using cyanidation occurs. The samples were used to evaluate cyanide contamination and the presence of cyanide degrading bacteria (CDB). Free cyanide (F-CN) was detected in all samples, with concentrations varying from 0.023 to 0.9 mg kg-1, and 0.7 - 23 mg L-1 in the soil and water samples, respectively. Potential CDB also were present in the samples. To test the effective F-CN degradation capacity of the isolated CDB species, the species were cultivated in growth media containing 40, 60 or 80 mg F-CN L-1, with or without nutrients, at pH 9.5 and at room temperature. More than 95% of F-CN was degraded within 25 h, and F-CN degradation was associated with bacterial growth and ammonium production. However, initial concentrations of F-CN higher than 100 mg L-1 inhibited bacterial growth and cyanide degradation. Abiotic tests showed that less than 3% of F-CN was removed by volatilization. Thus, the degradation of F-CN occurred predominately by biological mechanisms, and such mechanisms are recommended for remediation of contaminated soil and water.

The bacteria consortium used in the experiment described above exist in a Sahelian climate, which is characterized by a long hot and dry season. Because the bacteria are already adapted to the local climate conditions and show the potential for cyanide biodegradation, further applicability to other contaminated areas in West Africa, where illegal gold cyanidation is widespread, should be explored.

The Swiss Cooperation Agency was funded this research under the grant number 81016359/1.

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